Characterization of impressions created by turfgrass arthropods on clay models.
Lepidopteran pests such as fall armyworm, Spodoptera frugiperda (JE Smith), and black cutworm, Agrotis ipsilon Hufnagel (both Noctuidae), are serious problems of turfgrass (Poaceae) in the USA. Several predators in turfgrass systems attack lepidopteran larvae; however, their predaceous activity is rarely recorded, as they leave hardly any evidence. Predaceous activity can be studied using clay models, an approach still rarely employed in turfgrass. Thus, assays were conducted to determine the types of impressions that common turfgrass arthropods leave on clay models simulating lepidopteran larvae. Nine impression types were characterized after exposing 16 arthropod taxa in enclosed arenas in the laboratory and one taxon in the field to two sizes of clay models, including scratches, paired marks, pricks, deep distortions, disturbed surfaces, detached segments, granulated surfaces, dents, and elongated scratches. Most arthropods produced scratches and paired marks, whereas granulated surfaces and elongated scratches were produced by only a few of the selected arthropods. To ensure that the impressions were correctly identified, non-expert volunteers reviewed the impressions, and they were accurately identified in >85% of the responses. Video recordings of arthropod interactions were captured to determine the behavior of the arthropods during their first interaction with the clay models. Most arthropods first interacted with the terminal rather than the middle regions of the models. There were no differences between their interactions with the large or small models, and they used their mouthparts as often as their legs. Knowledge of the impression types caused by common arthropods will improve the utilization of the clay model technique for field studies in turfgrass. This could contribute to improved management of natural enemies as part of an integrated pest management approach.